"Typically left and right side tile installations are mirror images and these are not."
Space shuttle Discovery, STS-131 [mission specialist Clay Anderson is seen in the corner pilot-side window]. From ISS023-E-019907
They are perhaps the most easily recognizable tiles in space shuttle history. For shuttle watchers, when you see them, you know exactly which shuttle you are looking at. Only space shuttles Columbia and Enterprise are more recognizable. The four other shuttles — Challenger, Discovery, Atlantis and Endeavour — aside from their names being painted on them, appear in photos, on TV, film, and videos to be essentially the same. That is — except for those black tiles right below the corner pilot-side window on Discovery.
I noticed them immediately while watching the evening news back in October, 1983, when Discovery was rolled out for the first time at the Rockwell hanger in Palmdale, California, where she and all the shuttles underwent final assembly. I squinted and thought, "she has a tear in her eye." I've thought of those black tiles below the pilot's window as Discovery's "teardrop" ever since. Had they been located someplace else, perhaps I might have thought of them as a beauty mark. But, as a teardrop, it quickly became one of the reasons Discovery so endeared herself to me all these years. After all, any shuttle with a tear in her eye has to be pretty special. She has feelings.
People have historically given ships and planes (and often their cars) human attributes. They give them names. They christen them. They talk to them. They are typically thought of as female. I thought of Discovery's teardrop that way, too. Was she afraid of launching? After all, her very first attempt was rather scary — the first ever shutdown on the pad after main engine start. I could see how an infant shuttle might get a bit teary-eyed thinking about her first step. Or, later on, was it there for her lost sisters, Challenger, and then Columbia? She was always the one chosen to bravely lead the way after their loss. Or maybe it's just a tear of joy for the thrill of going into orbit, like when she did the first ever backflip in space?
Still, I've always wondered why those tiles below window No. 5 (if I'm correct) were there at all? On every other orbiter, those tiles are white. Discovery's alone are black. Whenever I happened to meet someone in the NASA shuttle program or an astronaut who had flown aboard Discovery, I would ask about them, but no one ever knew. That is, until Discovery was finally retired; with so many of Discovery's astronauts and all the NASA shuttle program people there at the Smithsonian's Udvar-Hazy Center in Virginia to commemorate Discovery's arrival, I knew this had to be my last, best chance to find out. And there, finally, I found the right person to ask. "You know, I don't think anyone's ever asked that question." "Now you have me curious. I'll try to find out."
A few months went by without hearing anything. But one day in July, 2012, just as I was starting to wonder if I'd ever know, the answer finally arrived in my email's inbox. (I will confess, my jaw dropped a bit when I saw some of the names "cc'd" as well.) It read:
Dear Mr. Cook,
You and I spoke at the Welcome Discovery event held in April at the National Air and Space Museum – Udvar Hazy Center. At that time you asked the following question: "Why does Discovery have [those] black tile[s] below the corner of window on the right side, like a tear drop?" Here is what we have been able to surmise after some research. The installation drawing for the tiles states tile to fabricate low-temperature reusable surface insulation (LRSI) (white) tiles. The Shuttle Drawing System only has the historical drawings back to Revision B (1983) - the Basic Revision and Revision A drawings are not available. Discovery’s three high-temperature reusable surface insulation (HRSI) (black) tiles were installed in 1983 as part of the vehicle’s original build. Those three black tiles have not been replaced since the original vehicle build. [Note: since receiving this email, I remembered originally there was a fourth tile, directly below the remaining three, just visible here (from Discovery STS 41-D - A new orbiter sets sail), that was also HRSI (black), and that gave their appearance a slight hook. That one has apparently been replaced.]
Typically left and right side tile installations are mirror images and these are not. The Tile information Processing System database has these three parts being LRSI tile (white) for Discovery. There is nothing in existing databases to suggest why HRSI tiles were installed in these locations on Discovery versus the LRSI tiles called for in existing drawings. As you have noted, Atlantis and Endeavour were fabricated with LRSI (white) tiles per drawing requirements. Columbia had a different configuration - diced LRSI (white) tiles, that were upgraded to LRSI tiles on an attrition basis.
So based on the above information, the following conclusion has been drawn: It is unlikely that a drawing change occurred post right side tile installation on Discovery. The most likely answer to your question is that the “tear drop” tiles were fabricated incorrectly during build and later accepted after being reviewed and determined to be acceptable for use as is.
I hope you find this information helpful. I appreciate your raising this question during our presentation in April. You have helped me to learn something new about Discovery.
[I wish I could identify the author by name because I am so very grateful for this individual's (and everyone's) time and effort in researching this. But because there were so many people were involved, I was asked to simply credit "NASA and the Space Shuttle Program."]
So, there you have it. Discovery was probably supposed to have gotten white tiles below the pilot's window, just like the other orbiters. But for some reason, most likely an error, these three tiles (and replaced fourth) were manufactured to be the more heat resistant HRSI (black) tiles, which were presumably nevertheless found to be acceptable for use on Discovery. In other words, Discovery's teardrop may have simply been a mistake. How the mistake happened will apparently remain a mystery. Perhaps it was destined. Still, that teardrop is as endearing to me now as it was when I first saw it on the evening news 30 years ago. Only now, when I see Discovery at the Udvar-Hazy Center, I'm pretty sure that teardrop is there because, well, she apparently just gets a bit emotional when people come to visit her.
Which is understandable, because I find I feel the same way in return. I have a feeling I'm not alone.
My thanks to NASA and the Space Shuttle Program.
- Jim Cook
" Those three black tiles have not been replaced since the original vehicle build. "